Furnace lining



March 30, 194s.

G. T. HUBBELL FUnNAcE Lmms Filed Feb. 18, 1942 All d l l l l l Il lining must be rem Patented Mar. 30, 1948 UNITED STATE FURNACE LINING George T. Hubbell, New H American Crucible Co.,

poration of Delaware aven, Conn., assignor to Shelton, Conn., a cor- Appllcation February 18, 1942, Serial No. 431,376 V (ci. 26e- 43) i claim. 1

'I'his invention relates to furnace linings or the like and the method of making the same, and more particularly to furnace linings made ofv a refractory material such as silicon carbide, and employed as a lining in a crucibie or' other type furnace where it must withstand the heat of the furnace flame.

In the past such linings have usually been made of blocks of refractory material, which blocks are laid together in the furnace and the joints or seams between them filled with a suitable cement. The renewal of a furnace lining has, therefore, been a tedious matter, as the old oved piece by piece and the the same manner and built up within the furnace. Moreover, it is usually the practice to apply a protective glaze to the surface of such blocks, and it is of course desirable that this glaze cover the entire surface of the furnace lining. This is impossible when the lining is built up of separate blocks, as the cement joints between the blocks cannot be covered by the glaze, although the blocks themselves may be so protected. There are, therefore, a numD ber of advantages to be gained from the manufacture of the entire furnace lining as a unitary, integral element so that it does not have to be built up of separate parts within the furnace, but may be readily and quickly installed as a unit, and may be removed in the same form when such removal is necessary.'

One object of the prese vide a one-piece unitary nace lining.

A further object of the invention is to provide an entire furnace lining as an integral element. the lining being provided with a suitable opening or openings as desired, of such form that the lining may be inserted into the furnace as a unit.

A still further object of the invention is the provision of a one-piece unitary furnace lining of hollow form, usually of greater height than either of its transverse dimensions, the entire surface of which is covered with a protective glazing composition. y

To these and other ends the invention consists in the novel features and combinations of parts to be hereinafter described and claimed.

In the accompanying drawing:

Fig. 1 is a vertical sectional view of a conventional type of furnace provided with a lining embodying my invention;

Fig. 2 is a top plan view of the furnace with the cover partly removed;

`lEig. 3 is an elevational sectional view of the new one installed in nt invention is to` prointegrally formed fur furnace lining and the mold in which the lining isformed;

Fig. 4 is -a horizontal sectional view on l-I of Fig. 3; and

Fig. 5 is an elevational view of the furnace lining.

To illustrate a lille preferred embodiment of my v invention I have shown in Fig. 1 of the draw- It will, of sents only furnaces in which the and is shown merely for purg one application of my invention. As shown, the furnace comprises a shell lil having a lining il of insulating material which may cover the walls and bottom. In the bottom of the furnace is a base i2, which will usually be formed of refractory material, upon which is supported a crucible rest I3 supporting a crucible it. Above the base block i2 stands the furnace lining l5, which is the subject of the present invention.

Any type of cover may be employed for the furnace. As shown, the shell ill is provided with a bracket it in which is pivotally mounted a vertically extending rod ilA having secured thereto a handleA i8 by which it may be turned. Also supported from the rod il is a ring or band. i@ carryingl the cover it, the weight of which is borne by the cables 2i carried 'by a bracket 22 at the upper end of the rod il. It will be under-1 stood that the cover itself will usually be form of refractory material, and as shown in Fig. 2, it may be swung to one side to open thefurnace by turning the pivot rod il by' means of the arm iii, so that the crucible may be placed in and removed from the furnace itself. It will be understood that the cover 263 will usually be proings a. furnace of conventional type.

course, be understood that this repre one of the many forms of lining can be made, poses of illustratin vided with a flame opening 23, and likewise a burner opening 2d is usually provided in the side wall of the furnace. As will be hereinafter explainedythis opening will communicate with an opening in the furnace lining to allow the insertion therethrough of a flame nozzle or the like. It will also be understood that, if desired, a slag opening may be provided in both the furnace wall and the furnace lining, although they are not shown in the present disclosure.

As shown in Fig. 5, the furnace lining i5 in this instance comprises a hollow body of cylindrical i form provided with a burner opening 25 which may be placed at any desired-point between the upper and lower ends of the lining. This opening will usually be obliquely disposed with respect to the diameter of the lining, so that the ame from the burner will be directed around the wall of the crucible within the furnace. It will also be understood that, while as shown the lining is of cylindrical form, it may be made of square or rectangular cross-section, or in any shape vor size suitable for the furnace in which it is to be employed. It will also be understood that it is made to fit a furnace in which it is to be used, so that the complete lining will be an integral unitary member. While the dimensions of the lining may vary according to the requirements of the furnace for which it is adapted, its height will generally be as great or greater than either of its horizontal or transverse dimensions.

When made in this way it may be placed in the furnace as a unit, and will be devoid of lateral or vertical joints, which will not only greatly facilitate the replacement of a furnace lining when replacementis necessary, but it will also result in a longer period of use.

After the lining is made and the opening 25 formed therein, it is usually covered by a glazing composition which may be sprayed upon its s'urface. This glazing composition is then burned upon the wall of the lining in a kiln, and the result is that the entire surface of the lining is covered with a hard glaze which protects it in various ways and prolongs its period of service.

In the manufacture of the lining shown in the present application, inner and outer cylinder forms 26 and 21 are preparedand placed upon a base or slab 28. The mix from which the lining is made is, as stated, of refractory material, usually having a silicon carbide base and a claybond, although any suitablevmix may be employed. The mix is placed between the forms 26 and 2l, as shown in Fig. 3, and tamped down until the space between the forms is completely filled. It is allowed to set for a period of approximately 20 hours in the air, at which time the mold forms may be removed. As the material shrinks to some extent in the setting, the molds may be slipped out from the lining itself. If desired, the molds of course may be made of sections, so that their removal from the product will be facilitated.

Upon removal from the mold, the lining, while set sufliciently to retain its form, is still relatively soft, and the burner opening 25 may be made therein in any suitable Way, as may also be made any other opening, such as a slag opening (not shown), for example. The lining is now permitted to air-set for several days, during which time the glazing composition is sprayed upon the walls thereof, as will be hereinafter set forth more particularly. This glazing composition is usually in two coats, the second one being applied after the first has been permitted to dry. After application of the glazing composition, the lining is placed in ar kiln and red at a temperature of approximately 2200 F. for a period of three to three and a half days. This not only completes the setting of the refractory mix from 1 which the lining is made, but also burns the glazing composition upon the lining so that it, in enect, becomes an integral part of the lining itself.

As stated, I prefer to use two coats of glazing composition, andV while the constituents and proportions of these constituents may vary to some extent, I find that the two compositions described below result in a glaze of superior qualities.

x For the first or base coat I employ approximately 60 pounds of a clay having a relatively low melting point, such as Richards clay, approx- 'imately 60 pounds of silicon carbide, approxi mately 'I1/2 pounds of silicate of soda, and about Y 6 pounds of dextrine, together with approximately 68 pounds of water. After the ingredients have been mixed and the water added, the entire mixture is ground in a suitable manner, such as in a ball mill, for example, so as to reduce the mixture to a fineness so that it can be sprayed upon the lining. The above proportions of materials may be varied to some extent. For example, the proportions of the four ingredients may vary from 40% to 55% of clay, 40% to 50% of silicon carbide. 3% to 8% silicate of soda, and

2% to 6% of dextrine. The water employed is approximately one-half of the weight of the other products.

For the second or finish coat I employ a mixture consisting of approximately 25% to 35% of Richards clay, approximately 5% to 9% of Albany slip, approximately 25% to 35% of Fritt, enamel No. 1100, and 30% to 40% of Pennsylv Vania flint No. mesh, and adding to the resulting mixture about two-thirds of its weight of water. That is, the water may vary from 60% to 75% of the combined weight of the other materials. I have found, for example, that a superior glaze for the second rcoat may be made by employing about 30 pounds of Richards clay, 7 pounds of Albany slip, 30 pounds of Fritt enamel, and 35 pounds of Pennsylvania flint clay. The Fritt enamel which I prefer to employ is essentially an alkali `boro-alumina, silicate,

dry ground so that approximately 14% of the powder is retained on a 200 mesh sieve.

When the lining is placed in the kiln after the application of the second coat of the glazing composition, the two coats will be fused and will be burned upon the lining itself and become integrated therewith. The result wil be a unitary, one-piece furnace lining completely covered by the glazing composition, and having over its entire area a glossy, smooth protective surface which lengthens its period of service and provides a lining which may be readily installed in or removed from a furnace with eort.

After the lining has been completed, it is installed in the furnace Joy being lowered through the top thereof. The lining may be provided with recesses or notches 30 in its lower edge in which may be received cables or ropes by which the lining may be conveniently handled during the lowering operation.

While I have shown and described a preferred embodiment of my invention and a preferred method of manufacturing the same, it will be understood that it is not to be limited to all of the details shown, but is capable of modification and variation within the spirit of the invention and within the scope of the claim.

' What I claim is:

A furnace comprising an outer shell open at the top and having a base therein adapted to support a crucible, a lining member resting freely on said base, said member comprising a preformed unitary cylindrical member open at theV top and ybottom and extending from said base to approximately the top of said shell, said a minimum of the inner surface of said member being glazed continuously over its entire area.

GEORGE T. HUBBELL.

REFERENCES CITED The following references are of record in they 111e of this patent:

UNITED STATES PATENTS Number Name l Date Bates July 31,- 1894 Locke May 16, 1905 Selden Sept. 12, 1916 Kunzler Nov. 19, 1918 Copland May 25, 1 920 Fulton Jan. 11, 1921 Funk Mar. 7, 1922 Number Number 10 135,241 332,701

Harvard,

15 McGraw-Hill BookCo., publishers, New York city, pages 244-250. 

